ES2672975T3 - Polymers initiated with amine and rigid polyurethane foam obtained from them - Google Patents

Abstract

A process for preparing a rigid polyurethane foam, comprising the following: a) forming a reactive mixture containing at least: 1) an amine-initiated polyol or a mixture of this with at least one other different polyol, provided that said mixture contains at least 5% by weight of the amine-initiated polyol, where the amine-initiated polyol has a variable average functionality between 3.3 and 4.0 and a hydroxyl equivalent weight of between 75 and 560, and the initiated polyol with amines is a reaction product of at least one C2-C4 alkylene oxide with an aminocylohexane-alkylamine initiator compound; 2) at least one polyether polyol having a functionality varying between 4.5 and 7 and a hydroxyl equivalent weight of 100 to 175; 3) at least one different amine-initiated polyol having a variable average functionality between 2.0 and 4.0 and a hydroxyl equivalent weight of between 100 and 225; 4) at least one physical hydrocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, fluorocarbon, dialkyl ether or fluorine substituted dialkyl ether blowing agent and 5) at least one polyisocyanate and b) subjecting the reaction mixture to conditions such that the reaction mixture expands and hardens to form a rigid polyurethane foam.

Description

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DESCRIPTION

Polymers initiated with amine and rigid polyurethane foam obtained from them

The present application claims the priority benefit of the US provisional application. with the number 60 / 898,367, filed on January 30, 2007.

The present invention relates to processes involving polyols, which are useful for manufacturing rigid polyurethane foams, as well as rigid foams made from such polyols.

Rigid polyurethane foams have been widely used for several decades, as insulating foam in household appliances and other applications, as well as, for various other uses. These foams are prepared in a reaction of a polyisocyanate and one or more polyol, polyamine or amino alcohol compounds. The polyol, polyamine or amino alcohol compounds may be characterized by having equivalent weights per isocyanate reactive group in a range of up to approximately 300 and an average greater than three hydroxyl and / or amino groups per molecule. The reaction is carried out in the presence of a blowing agent that generates a gas, as the reaction proceeds. The gas expands the reaction mixture and imparts a cellular structure.

Originally, the blowing agent of choice was a "hard" chlorofluorocarbon (CFC), such as trichlorofluoromethane or dichlorodifluoromethane. These CFCs were processed very easily and produced a foam with very good thermal insulation properties. However, CFC blowing agents have been gradually eliminated due to environmental issues.

CFCs have been replaced by other blowing agents, such as hydrofluorocarbons, low boiling hydrocarbons, hydrochloroflurocarbons, ether compounds and water (which reacts with isocyanates to generate carbon dioxide). On their greatest mars, these alternative blowing agents are less effective thermal insulators than their predecessors, the CFCs. The ability of a foam to provide thermal insulation is often expressed as a “k factor,” which is a measure of the amount of heat that is transferred through the foam per unit area per unit time, considering the thickness of the foam and the difference in temperatures applied throughout the thickness of the foam. Foams produced using alternative blowing agents tend to have higher k factors than those produced using "hard" CFC blowing agents. This has forced producers of rigid foams to modify the formulations of their foams in other ways, in order to compensate for the loss of thermal insulation values resulting from changes in the blowing agent. Many of these modifications focus on reducing the size of foam cells. Smaller cells tend to offer better thermal insulation properties.

It has been found that modifications to a rigid foam formulation that improve the k factor tend to affect the processing characteristics of the formulation in an undesired manner. The curing characteristics of the formulation are important, especially in the applications of pouring in situ, such as the foam of household appliances. Refrigerator and freezer cabinets, for example, are usually isolated by partially assembling an outer shell and inner liner and keeping them in position so that a cavity is formed between them. This is often done using a mounting device or other device. The formulation for the foam is introduced into the cavity, where it expands to fill it. The foam provides thermal insulation and imparts structural resistance to assembly. The way in which the formulation for the foam is cured is important in at least two aspects. First, the foam formulation must cure quickly, to form a dimensionally stable foam, so that the finished cabinet can be removed from the mounting device. This feature is usually called "demold" time and directly affects the speed at which cabinets can be produced.

On the other hand, the hardening characteristics (curing9 of the system affect a property known as “flow rate” or simply “flow.” A foam formulation expands to a certain density (known as' development density) free ') if you are allowed to expand with minimal restrictions. When the formulation must fill the cabinet of a refrigerator or freezer, its expansion is somewhat restricted in several ways. The foam should expand primarily in a vertical (rather than horizontal) direction. ) within a narrow cavity As a result, the formulation must expand against a significant amount of its own weight.The foam formulation must also flow around the corners and into all portions of the wall cavities. on the other hand, the cavity often has little or no ventilation and, therefore, the atmosphere inside the cavity exerts pressure Additional on the expanding foam. Due to these restrictions, a larger amount of formulation is needed for the foam to fill the cavity than is expected according to the free development density alone. The amount of foam formulation necessary to minimally fill the cavity can be expressed as a minimum filling density (the weight of the formulation divided by the volume of the cavity). The ratio of the minimum filling density to the free development density is the flow rate. The flow rate is ideally 1.0, but is in the order of 1.2 to 1.8 in commercially practical formulations. A lower flow rate is preferred, all other things being equal, because the costs of the raw materials are better when a lower foam weight is needed.

Modifications to the formulations for foams that favor a low factor tend to have an adverse effect on the time of demoulding, the flow rate or both. Therefore, although formulations that closely resemble conventional CFC-based formulations have been developed as far as the k factor is concerned, the overall cost of using these formulations is often higher, due to lower productivity (as a consequence of the longer demoulding times), at higher raw material costs (as a consequence of the higher flow rate) or for both reasons.

What is desired is a formulation for a rigid foam that provides a low-k foam with a low flow rate and a short release time.

This description refers, in one aspect, to a polyol initiated with amines having an average functionality of 10 hydroxyl ranging from 3.3 to 4.0, where the polyol is a reaction product of at least one C2- alkylene oxide C4 with an aminocyclohexane-alkylamine initiator compound.

The invention consists of a process for preparing a rigid polyurethane foam, comprising the following: a) forming a reactive mixture containing at least:

1) a polyol initiated with amines or a mixture thereof with at least one other polyol, at least one, with the proviso that said mixture contains at least 5% by weight of the polyol initiated with amines, where the polyol initiated with amines

it has a variable average functionality between 3.3 and 4.0 and an equivalent hydroxyl weight of between 75 and 560, and where the polyol initiated with amines is a reaction product of at least one C2-C4 alkylene oxide with a compound aminocylohexane-alkylamine initiator;

2) at least one polyether polyol having a variable functionality between 4.5 and 7 and an equivalent hydroxyl weight of

20 100 to 175;

3) at least one polyol started with different amines, which has a variable average functionality between 2.0 and 4.0 and an equivalent hydroxyl weight of between 100 and 225;

4) at least one physical hydrocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, fluorocarbon, dialkyl ether or fluorine substituted dialkyl ether blowing agent and

25 5) at least one polyisocyanate and

subject the reaction mixture to conditions such that the reaction mixture expands and hardens to form a rigid polyurethane foam.

In another aspect, the invention consists of a rigid foam manufactured in accordance with the above processes.

It has been found that formulations for rigid foams that include the polyol initiated with amines described above at 30 times denote desirable hardening characteristics (as indicated by the flow rate of less than 1.8) and for the short release times and that they harden to form a foam with excellent thermal insulation properties (i.e., low k factor). These advantages are observed in particular when the amine-initiated polyol of the invention is used in a mixture containing one or more other polyols, which have a hydroxyl functionality varying between 4 and 8 and an equivalent hydroxyl weight of 75 to 200 .

The amin-initiated polyol is a polyether that is prepared from at least one aminocyclohexane-alkylamine initiator compound. For the purposes of this invention, an initiator compound of

"Aminocyclohexane-alkylamine" is one that has a cyclohexane group that is substituted in the cyclohexane ring with a primary amino group (-NH2) and that is also substituted in the cyclohexane group with at least one aminoalkyl group - and preferably, only with one. The aminoalkyl group may be represented as - (CR2) m-NH2, where 40 each R is independently hydrogen or C1-C4 alkyl, and m is a number ranging from 1 to 8. Each R is preferably independently hydrogen or methyl The primary amino group and the aminoalkyl group or groups may be in the ortho, meta or for each other positions, and may be in the cis (both on the same side of the ring) or trans positions (located on opposite sides of the ring) some respect others. The cyclohexane ring may also contain an inert substitution. An "inert" substitution is a substitution that: (1) is not reactive with an alkylene oxide under alkoxylation conditions (as described in more detail below), (2) is not reactive with isocyanate groups and (3) is not significantly affects the ability of the compound to

aminocyclohexane-alkylamine of alkoxylate and of the resulting polyol reacting with a polyisocyanate to form urethane bonds. The inert substitution includes the hydrocarbyl substitution such as alkyl, alkenyl,

alkynylaryl, alkyl substituted with aryl, cycloalkyl and the like, ether groups, tertiary amino groups and the like. Be

50 prefers that any substituent group that may be present is C1-C4 alkyl, especially methyl. It is especially preferred that the cyclohexane ring has a methyl substitution in the carbon atom to which the amino group is attached.

It is possible to use mixtures of two or [SIC] initiator compounds, as described. The initiators of the preceding structure may be presented in two or more diastereoisomeric forms. In these cases, it can be used

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any of the diastereoisomeric forms or mixtures of any two or more of the diastereoisomeric forms. A class of aminocyclohexane-alkylamine compounds includes those represented by formula I:

image 1

in which R1 is C1-C4 alkyl and R and m are as defined above. Each R group in structure I is preferably independently hydrogen or methyl, and R1 is preferably methyl. In structure I, the group (CR2) m-NH2 may be ortho, meta or for the amino group directly attached to the cyclohexane ring. The NH2y (CR2) m-NH2 groups in structure I may be in the cis or trans positions, relative to each other. In structure I, the cyclohexane carbon atoms may contain inert substituent groups, in addition to the -NH2, -R1 and - (CR2) m-NH2 groups shown. A preferred starter compound corresponding to structure I is cyclohexanemethanamine, 4-amino-a, a, 4-trimethyl- (9Cl), which is also known as p-mint-1,8-diamine or 1,8-diamino-p - ash. This compound comes in two diastereoisomeric forms, as shown below:

Y

It is possible to use any of the diastereoisomeric forms or a mixture of both.

A second type of aminocyclohexane-alkylamine initiator corresponds to structure II:

image2

image3

image4

in which R, R1 and m are as defined above. As in structure I, each group R in structure II is preferably independently hydrogen or methyl, and Rres preferably methyl. In structure II, the group - (CR2) m-NH2 may be ortho, meta or for the amino group directly attached to the cyclohexane ring. The groups -NH2 and - (CR2) m-NH2 in structure II may be in the cis or trans positions, with respect to each other. In structure II, the cyclohexane carbon atoms may contain inert substituent groups in addition to the -NH2, -R1 and - (CR2) m-NH2 groups shown. An especially preferred initiator compound corresponding to structure II is 5-amino-1,3,3-trimethylcyclohexane-methylamine, which is commonly known as isophorondiamine. Isoforondiamine also occurs in two diastereoisomeric forms, as represented below:

image5

Y

image6

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Again, it is possible to use any of these forms or a mixture of them.

Aminocyclohexane-alkylamine compounds tend to contain small amounts (typically, less than 3% by weight) of impurities, which tend to be mainly other amine or diamine compounds. These commercial materials are suitable as initiators in the present invention.

The initiator compound is reacted with at least one C2-C4 alkylene oxide, to produce the initiated polyol with amines useful in the processes of the invention. The alkylene oxide may be ethylene oxide, propylene oxide, 1,2- or 2,3-butylene oxide, tetramethylene oxide or a combination of two or more of them. If two or more alkylene oxides are used, they can be incorporated into the initiator compound simultaneously (to form a random copolymer) or sequentially (to form a block copolymer). Generally, butylene oxide and tetramethylene oxide are less preferred. Ethylene oxide, propylene oxide and mixtures thereof are more preferred. Mixtures of ethylene oxide and propylene oxide may contain oxides in any proportion. For example, a mixture of ethylene oxide and propylene oxide may contain from 10 to 90% by weight of ethylene oxide, preferably, from 30 to 70% by weight of ethylene oxide or from 40 to 60% by weight of ethylene.

To the initiator is added the sufficient amount of one or more alkylene oxides, in order to produce a polyol having an average hydroxyl functionality varying between 3.3 and up to as much as 4.0 hydroxyl groups / molecule. A preferred average hydroxyl functionality for the polyol is 3.7 to 4.0. A polyol useful in the processes of the invention which is useful for preparing a rigid polyurethane foam conveniently has an equivalent hydroxyl weight of between 75 and 560. A preferred hydroxyl equivalent weight for the production of rigid foams ranges from 90 to 175 , and the most preferred hydroxyl equivalent weight for the production of rigid foams is 100 to 130.

The alkoxylation reaction is conveniently carried out by forming a mixture of the alkylene oxide (s) and the initiator compound, and subjecting the mixture to conditions of high temperature and superratmospheric pressure. The polymerization temperatures can vary, for example, from 110 to 170 ° C, and the pressures can be located, for example, between 2 and 10 bar (200 to 1000 kPa). A catalyst can be used, in particular if more than one mole of alkylene oxide / s per equivalent of amine hydrogen is added to the initiator compound. Suitable alkoxylation catalysts include strong bases, such as alkali metal hydroxides (sodium hydroxide, potassium hydroxide, cesium hydroxide, for example), as well as so-called double metal cyanide catalysts (of which the most prominent are zinc hexacyanocobaltate complexes). The reaction can be carried out in two or more stages, where no catalyst is used in the first stage and 0.5 to 1.0 mol of alkylene oxide is added to the initiator per equivalent of amine hydrogens, to which follows one or more subsequent steps in which additional alkylene oxide is incorporated, in the presence of a catalyst as described. Once the reaction is complete, the catalyst can be deactivated and / or removed. It is possible to remove the metal hydroxide catalysts, leave them in the product or neutralize them with an acid, leaving the residues in the product. Residues of the two metal cyanide catalysts can remain in the product, but they can also be removed, if desired.

Preferred amin-initiated polyols are: (a) the reaction product of isophorondiamine or 1,8-diamino-p-menthane with ethylene oxide, (b) the reaction product of isophorondiamine or 1,8-diamino-p- Methane with propylene oxide and (c) the reaction product of isophorondiamine or 1,8-diamino-p-methane with a mixture of between 30 and 70% in mol of ethylene oxide and between 70 and 30% in mol oxide of propylene, which in each case has a hydroxyl functionality varying between 3.3 and 4.0, especially from 3.7 to 4.0 and an equivalent weight of hydroxyl between 90 and 175, in particular, 100 to 130.

The polyol initiated with amines useful in the processes of the invention is useful for preparing a rigid polyurethane foam, in particular, when its equivalent hydroxyl weight ranges from 75 to 560. The rigid polyurethane foam is prepared from a composition polyurethane forming agent containing at least: (1) the polyol initiated with amines, optionally, in combination with one or more different polyols, (2) at least one organic polyisocyanate and (3) at least one physical blowing agent, according to It is described in more detail below.

The amin-initiated polyol useful in the processes of the invention conveniently constitutes at least 5% by weight of all polyols present in the polyurethane-forming composition. Below this level, the benefits of using polyol are scarce. The amin-initiated polyol useful in the processes of the invention may be the only polyol present in the polyurethane forming composition. However, it is envisaged that in most cases it will be used in a mixture containing at least one other polyol and that the polyol initiated with amines useful in the processes of the invention constitutes between about 5 and about 75% by weight of the mixture of polyols. For example, the amin-initiated polyol useful in the processes of the invention may constitute between about 10 and 60%, by weight of the polyol mixture or between about 10 and about 50% by weight of the polyol mixture .

When a mixture of polyols is used, the mixture of polyols preferably has an average of about 3.5 to 7 of hydroxyl groups / molecule and an average equivalent weight of variable hydroxyl between about 90 and about 175. All individual polyols within the mix can have a functionality and / or

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an equivalent weight outside those intervals, if the mixture satisfies these parameters. Water is not considered when determining the functionality or equivalent weight of a mixture of polyols.

An average hydroxyl functionality for a mixture of polyols that is more preferred varies between about 3.8 and about 6 hydroxyl groups / molecule. An average hydroxyl functionality for a more preferred polyol mixture still varies between about 3.8 and about 5 hydroxyl groups / molecule. An average equivalent weight of hydroxyl for a more preferred polyol mixture ranges from about 110 to about 130.

Suitable polyols that can be used in conjunction with the amin-initiated polyol useful in the processes of the invention include polyether polyols, which are conveniently prepared by polymerizing an alkylene oxide in an initiator compound (or mixture of initiator compounds) which has several active hydrogen atoms. The initiator compound (s) may include alkylene glycols (eg, ethylene glycol, propylene glycol, 1,4-butane diol, 1,6-hexanediol and the like), glycol ethers (such as diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol and the like), glycerin, trimethylolpropane, pentaerythritol, sorbitol, sucrose, glucose, fructose or other sugars and the like. A portion of the initiator compound may be one containing primary and / or secondary amino groups, such as ethylenediamine, hexamethylenediamine, diethanolamine, monoethanolamine, N-methyldiethanolamine, piperazine, aminoethylpiperazine, diisopropanolamine, monoisopropanolamine, methanolamine, dimethanolamine (dimethanolamine, dimethanolamine (dimethanolamine) ) and the like. Polyols initiated with amines of these types tend to be autocatalytic in some ways. The alkylene oxides used to make the additional polyol (s) are as described above with respect to the polyol initiated with amines useful in the processes of the invention. The alkylene oxide of choice is propylene oxide, or a mixture of propylene oxide and ethylene oxide.

Polyester polyols can also be used as additional polyol, but in general they are less preferred, as they tend to have lower functionalities. Polyester polyols include the reaction products of polyols, preferably diols, with polycarboxylic acids or their anhydrides, preferably, dicarboxylic acids or dicarboxylic acid anhydrides. The polycarboxylic acids or anhydrides may be aliphatic, cycloaliphatic, aromatic and / or heterocyclic and may be substituted, such as with halogen atoms. Polycarboxylic acids can be unsaturated. Examples of these polycarboxylic acids include succinic acid, adipic acid, terephthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride, maleic acid, maleic acid anhydride and fumaric acid. The polyols used to make the polyester polyols include ethylene glycol, 1,2- and 1,3-propylene glycol, 1,4- and 2,3-butanediol, 1,6-hexanediol, 1,8-octandiol, neopentyl glycol, cyclohexan- dimethanol, 2-methyl-1,3-propanediol, glycerin, trimethylol-propane, 1,2,6-hexantriol, 1,2,4-butantriol, trimethylolethane, pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, dibutylene glycol and the like.

The polyol initiated with amines useful in the processes of the invention is used as a mixture with at least one other polyether polyol, which has a variable average functionality between 4.5 and 7 hydroxyl groups per molecule and an equivalent hydroxyl weight of 100 to 175. The other polyether polyol can be, for example, a polyether initiated with sorbitol or sucrose / glycerin. The polyol initiated with amines useful in the processes of the invention may constitute between 10 and 70% of the weight of the mixture in this case. Examples of suitable sorbitol-or sucrose / glycerin initiated polyethers that can be used include Voranol® 360, Voranol® RN411, Voranol® RN490, Voranol® 370, Voranol® 446, Voranol® 520, Voranol® 550 and Voranol® polyols 482, all of them from Dow Chemical.

In a preferred embodiment, the amin-initiated polyol useful in the processes of the invention is employed in a mixture of polyols that also contains at least one different polyether polyol having a variable average functionality between 4.5 and 7 hydroxyl groups per molecule. and an equivalent hydroxyl weight of 100 to 175, and which does not start with amines, and at least one other polyol started with different amines having a varying average functionality between 2.0 and 4.0 (preferably, between 3.0 and 4.0) and an equivalent hydroxyl weight of between 100 and 225. The other polyol initiated with amines can be initiated, for example, with ammonia, ethylenediamine, hexamethylene diamine, diethanolamine, monoethanolamine, N-methyldiethanolamine, piperazine, aminoethylpiperazine, diisopropanolamine, monoisopropanolamine , methanolamine, dimethanolamine, toluendiamine (all isomers) and the like. In this case, polyols initiated with ethylenediamine and toluendiamine are preferred. The polyol mixture may contain, between 5 and 50% by weight of the polyol initiated with amines useful in the processes of the invention; between 20 and 70% by weight of the polyol not initiated with amines and between 2 and 20% by weight of the other polyols initiated with amines. The polyol mixture may contain up to 15% by weight of another polyol, which does not start with amines and which has a hydroxyl functionality of 2.0 to 3.0 and an equivalent hydroxyl weight of between 90 and 500, preferably, between 200 and 500. Specific examples of mixtures of polyols such as those just described include a mixture of between 5 and 50% by weight of the polyol initiated with amines useful in the processes of the invention, between 20 and 70 % of a polyether-polyol initiated with sorbitol or sucrose / glycerin that has a variable average functionality between 4.5 and 7 hydroxyl groups per molecule and an equivalent hydroxyl weight of 100 to 175, 2 to 20% by weight of an ethylenedipolol initiated with amines, having an equivalent weight of between 100 and 225, and from 0 to 15% by weight of a polyol not initiated with amines having a variable functionality between 2.0 and 3.0 and an equivalent weight of hydroxyl of between 200 and 500.

Mixtures of polyols such as those described can be prepared by manufacturing the constituent polyols individually and then mixing them together. Alternatively, mixtures of polyols can be prepared by forming a mixture of the respective initiator compounds and then alkoxylating the initiator mixture to form the mixture of polyols directly. Such "co-initiated" polyols can be prepared using

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aminocyclohexane-alkylamine and other amine as initiators, to form a mixture of polyols initiated with amines. It is also possible to use combinations of these approaches.

The polyurethane forming composition contains at least one organic polyisocyanate. The organic polyisocyanate or a mixture thereof advantageously contains an average of at least 2.5 isocyanate groups per molecule. A preferred isocyanate functionality ranges between about 2.5 and about 3.6 or between about 2.6 and about 3.3 isocyanate groups / molecule. The polyisocyanate or a mixture thereof, advantageously, has an equivalent isocyanate weight of between about 130 and 200. This is preferably from 130 to 185 and, more preferably, from 130 to 170. These functionality and weight values equivalent should not necessarily be applied with respect to the individual polyisocyanate present in a mixture, as long as the mixture as a whole satisfies these values.

Suitable polyisocyanates include aromatic, aliphatic and aliphatic cycle polyisocyanates. In general, aromatic polyisocyanates are preferred. Exemplary polyisocyanates include, for example, m-phenylene diisocyanate, 2,4- and / or 2,6-toluene diisocyanate (TDI), the various isomers of diphenylmethanediisocyanate (MDI), hexamethylene-1,6-diisocyanate, tetramethylene -1,4-diisocyanate, cyclohexane-1,4-diisocyanate, hexahydrotoluen-diisocyanate, hydrogenated MDI (H12 MDI), naphthylene-1,5-diisocyanate, methoxyphenyl-2,4-diisocyanate, 4,4'-biphenylene diisocyanate , 3,3'-dimethyloxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4 ', 4 "-triphenylmethane diisocyanate, polymethylene polyphenyl isocyanates, polymethylene polyphenyl -hydrogenated polyisocyanates, toluene-2,4,6-triisocyanate and 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate. Preferred polyisocyanates are so-called polymeric MDI products, which are a mixture of polymethylene polyphenylene polyisocyanates in monomeric MDI. In particular, suitable polymeric MDI products have a free MDI content of between 5 and 50% by weight, more preferably, 10 to 40% by weight. These polymeric MDI products are marketed through The Dow Chemical Company, under the PAPI® and Voranate® brands.

An especially preferred polyisocyanate is a polymeric MDI product having an average isocyanate functionality varying between 2.6 and 3.3 isocyanate groups / molecule and an equivalent isocyanate weight between 130 and 170. Suitable commercial products of this type include the following: PAPI ™ 27, Voranate ™ M229, Voranate ™ 220, Voranate ™ 290, Voranate ™ M595 and Voranate ™ M600, all of them from Dow Chemical.

Prepolymers and quasi-prepolymers (mixtures of prepolymers with unreacted polyisocyanate compounds) terminated with isocyanate can also be used. These are prepared by reacting a stoichiometric excess of an organic polyisocyanate with a polyol, such as the polyols described above. Suitable methods for preparing these prepolymers are well known. Said prepolymer or quasi-prepolymer preferably has an isocyanate functionality varying between 2.5 and 3.6 and an equivalent isocyanate weight between 130 and 200.

The polyisocyanate is used in an amount sufficient to provide an isocyanate index of between 80 and 600. The isocyanate index is calculated as the number of reactive isocyanate groups provided by the polyisocyanate component divided by the number of reactive isocyanate groups present in the polyurethane-forming composition (including those contained by isocyanate reactive blowing agents, such as water) and multiplying by 100. Water is considered to have two reactive isocyanate groups per molecule for the purpose of calculating the isocyanate index. A preferred isocyanate index ranges between 90 and 400 and a more preferred isocyanate index ranges from 100 to 150.

The blowing agent employed in the polyurethane-forming composition includes at least one physical blowing agent, which is a hydrocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, fluorocarbon, dialkyl ether or fluorine substituted dialkyl ethers or a mixture of two or more of them. Blowing agents of these types include propane, isopentane, n-pentane, n-butane, isobutene, isobutene, cyclopentane, dimethyl ether, 1,1-dichloro-1-fluoroethane (HCFC-141b), chlorodifluoromethane (HCFC-22), 1 -chloro-1,1-difluoroethane (HCFC-142b), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1,3,3-pentafluorobutane (HFC-365mfc), 1,1- difluoroethane (HFC-152a),

1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) and 1,1,1,3,3-pentafluoropropane (HFC-245fa). Hydrocarbon and hydrofluorocarbon blowing agents are preferred. Generally, it is also preferred to include water in the formulation, in addition to the physical blowing agent.

The blowing agent (s) are preferably used in a sufficient amount such that the formulation hardens to form a foam whose molded density varies between 16 and 160 kg / m3, preferably between 16 and 64 kg / m3 and, in particular, from 20 to 48 kg / m3. To achieve these densities, the hydrocarbon or hydrofluorocarbon blowing agent is conveniently used in an amount ranging from about 10 to about 40, preferably, between an approximate value of 12 and an approximate value of 35 parts by weight per 100 parts by weight polyol / s. Water reacts with isocyanate groups to produce carbon dioxide, which acts as an expansion gas. Conveniently, the water is used in an amount in the range of 0.5 to 3.5, preferably 1.5 to 3.0 parts by weight per 100 parts by weight of polyol / s.

The polyurethane forming composition will generally include at least one catalyst for the reaction of the polyol and / or water with the polyisocyanate. Suitable urethane-forming catalysts include those described in US Pat. UU. with the number 4,390,645 and in the patent document with the

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No. WO 02/079340, both incorporated herein by reference. Representative catalysts include tertiary amine and phosphine compounds, chelates of various metals, acidic metal salts of strong acids; strong bases, alcoholates and phenolates of various metals, salts of organic acids with a variety of metals, organometallic derivatives of tetravalent tin, As, Sb and Bi trivalent and pentavalent and metal carbonyls of iron and cobalt.

Generally, tertiary amine catalysts are preferred. Tertiary amine catalysts include the following: dimethylbenzylamine (such as Desmorapid® DB, from Rhine Chemie), 1,8-diaza (5,4,0) undecano-7 (such as Policat® SA-1, from Air Products), pentamethyldiethylenetriamine (such as Policat® 5, from Air Products), dimethylcyclohexylamine (such as Policat® 8, from Air Products), triethylenediamine (such as Dabco® 33LV from Air Products), dimethyl-ethiamine, n-ethyl-morpholine , N-alkyl dimethylamine compounds, such as N-ethyl-N, N-dimethylamine and N-cetyl-N, N-dimethylamine, N-alkyl morpholine compounds, such as N-ethyl morpholine and N-coco -morpholine, and the like. Other useful tertiary amine catalysts include those marketed by Air Products, under the brands Dabco® NE1060, Dabco® NE1070, Dabco® NE500, Dabco® TMR-2, Dabco® TMR 30, Policat® 1058, Policat® 11, Policat 15, Policat® 33, Policat® 41 and Dabco® MD45, and those marketed by Huntsman, with the brands ZR 50 and ZR 70. In addition, as catalyst materials, certain amines initiated polyols can be used here, including those described in the patent document with the number WO 01/58976 A. It is possible to use mixtures of two or more of the foregoing.

The catalyst is used in catalytically sufficient amounts. For preferred tertiary amine catalysts, a suitable amount of catalysts varies between about 1 and about 4 parts, especially between about 1.5 and about 3 parts of tertiary amine catalyst / s per 100 parts by weight of the o of the polyols.

The polyurethane-forming composition also preferably contains at least one surfactant, which helps stabilize the cells of the composition as the gas evolves, to form bubbles and expand the foam. Examples of suitable surfactants include alkali metal salts and fatty acid amine salts, such as sodium oleate, sodium stearate, sodium ricinolates, diethanolamine oleate, diethanolamine stearate, diethanolamine ricinoleate and the like; alkali metal and amine salts of sulfonic acids, such as dodecylbenzenesulfonic acid and dynaphthylmethane disulfonic acid; ricinoleic acid; polymers or copolymers of siloxane-oxalkylene and other organopolysiloxanes; oxethylated alkylphenols (such as Tergitol NP9 and Triton X100, from The Dow Chemical Company); oxyethylated fatty alcohols, such as Tergitol 15-S-9, from The Dow Chemical Company; paraffinic oils; Castor oil; esters of ricinoleic acid; red turkey oil; peanut oil; paraffins; fatty alcohols; dimethyl polysiloxanes and oligomeric acrylates with polyoxyalkylene and fluoroalkane side groups. These surfactants are generally used in an amount of 0.01 to 6 parts by weight, based on 100 parts by weight of the polyol.

In general, the types of organosilicone surfactants are preferred. A wide variety of these organosilicone surfactants are available in the market, including those sold by Goldschmidt under the Tegostab® brand (such as Tegostab surfactants B-8462, B8427, B8433 and B- 8404), which are sold by OSi Specialties, with the Niax® brand (such as Niax® L6900 and L6988 surfactants), as well as various surfactant products marketed by Air Products and Chemicals, such as DC-193, DC-198, DC-5000, DC-5043 and DC- 5098 surfactants.

In addition to the aforementioned ingredients, the polyurethane-forming composition may include various auxiliary components, such as fillers, dyes, masking agents, flame retardants, biocides, antioxidants, UV stabilizers, antistatic agents, viscosity modifiers and the like.

Examples of suitable flame retardants include phosphorus compounds, halogen-containing compounds and melamine.

Examples of fillers and pigments include calcium carbonate, titanium dioxide, iron oxide, chromium oxide, azo / diazo dyes, phthalocyanines, dioxazines, rigid recycled polyurethane foam and carbon black.

Examples of UV stabilizers include hydroxybenzotriazoles, zinc dibutyl thiocarbamate, tertiary 2,6-di-butyl catechol, hydroxybenzophenones, hindered amines and phosphites.

Except for fillers, the above additives, in general, are used in small amounts, such as 0.01% to 3%, each based on the weight of the polyurethane formulation. The fillers can be used in amounts as high as 50% by weight of the polyurethane formulation.

The polyurethane-forming composition is prepared by joining the various components together, under conditions that allow the reaction of the polyol (s) and the isocyanates (s); The blowing agent generates a gas and the composition expands and hardens. All components (or any sub-combination thereof), except polyisocyanate, can be pre-mixed in a formulated polyol composition, if desired, which is then mixed with the polyisocyanate when the foam should be prepared. The components can be preheated, if desired, but usually this is not necessary and the components can be joined together at a temperature close to ambient (~ 22 ° C) to carry out the reaction. Normally it is not necessary to apply heat to the composition to

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boost hardening, but if desired this can also be done.

The invention is particularly useful in "pouring in situ" applications, where the polyurethane-forming composition is dispensed into a cavity and foams into the cavity, to fill it and provide structural and / or insulating thermal attributes to a mounting. Nomenclature "Poured in situ" refers to the fact that the foam is generated at the point that is needed, instead of generating it at a previous stage, and then placing it in its place, in a separate manufacturing stage. Pouring processes in situ are normally used in the manufacture of household appliances, such as refrigerators, freezers and refrigerators, as well as similar products that have foam-containing walls for thermal insulation. The presence of the polyol initiated with amines in the polyurethane-forming composition tends to confer good fluidity and short demolding times to the formulation, while producing a low-k foam.

Most conveniently, the walls of household appliances such as refrigerators, freezers and refrigerators are insulated in accordance with the invention, first assembling an outer shell and the inner liner together, so that a cavity is formed between the housing and the liner. inside. The cavity defines the space to be isolated, as well as the dimensions and shape of the foam that is produced. Typically, the carcass and inner liner are glued together in some way, for example, by welding, fusion adhesion or by using some adhesive (or some combination thereof) before the introduction of the foam formulation. The housing and inner liner can be held or held in the correct relative positions using a mounting device or other device. One or more entries for the cavity are provided, through which it is possible to introduce the formulation for the foam. Generally, one or more outlets are provided to allow air to escape from the cavity, as it is filled with the foam formulation and the foam formulation expands.

The construction materials of the housing and the inner lining are not particularly critical, as long as they can withstand the hardening conditions and the expansion reactions of the foam formulation. In most cases, construction materials are selected in relation to specific performance attributes that are sought in the final product. In general, metals such as steel are used for the housing, particularly in large appliances, such as freezers or refrigerators. Plastics, such as polycarbonates, polypropylene, polyethylene-styrene-acrylonitrile resins, acrylonitrile-butadiene-styrene resins or high-impact polystyrene are most often used to make smaller appliance housings (such as refrigerators) or for those in Those that low weight is important. The inner lining may be a metal, but it is more common that it is a plastic, as described above.

Then the foam formulation is introduced into the cavity. The various components of the foam formulation are mixed together, and the mixture is quickly introduced into it, where the components react and expand. It is common to previously mix the polyol (s) together with the water and the blowing agent (and often, the catalyst and / or the surfactant as well) to produce a formulated polyol. The formulated polyol can be stored until it is time to prepare the foam, at which time it is mixed with the polyisocyanate and introduced into the cavity. In general, it is not necessary to heat the components before inserting them into the cavity, nor is it usually necessary to heat the formulation inside the cavity to drive hardening, although either of these stages or both can be implemented if desired. The housing and the inner lining can act as a heat sink in certain cases, and eliminate heat from the formulation for the foam that reacts. If necessary, the housing and / or the inner lining can be heated to a certain extent (for example, up to 50 ° C and more typically 35-40 ° C) to reduce this effect of the heatsink or to boost hardening.

A sufficient amount of the formulation for the foam is introduced so that, after its expansion, the resulting foam fills said portions of the cavity where the foam is desired. Most commonly, essentially the entire cavity is filled with foam. In general, it is preferred to "overflow" the cavity slightly, introducing more foam formulation than is minimally needed to fill the cavity, thereby increasing the density of the foam slightly. Overflowing the cavity offers benefits, such as better dimensional stability of the foam, especially in the post-demolding period. In general, the cavity is exceeded by 4 to 20% by weight. The final density of the foam for most appliance applications varies, preferably, in the range of between 28 and 40 kg / m3.

After the formulation for the foam has expanded and has been sufficiently hardened to be dimensionally stable, the resulting assembly can be "unmold" by removing it from the mounting device or other support that is used to hold the housing and the inner lining in their correct relative positions. Short release times are important for the appliance industry, since these shorter release times allow more parts per unit of time to be manufactured in a given piece of manufacturing equipment.

The release times can be evaluated as follows: a 28-liter Brett "jumbo" mold, coated with a release agent is conditioned to a temperature of 45 ° C. 896 g ± 4 g of a foam formulation are injected into the mold, to obtain a foam with a density of 32 kg / m3. After a period of 6 minutes, the foam is removed from the mold and its thickness is measured. After another 24 hours, the thickness of the foam is measured again. The difference between the thickness after 24 hours and the initial thickness is an indication of

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expansion after foam demoulding. The release time is considered long enough if the post-release expansion does not exceed 4 mm in this test.

As mentioned, flow is another important attribute of the formulation for foam. For the purposes of this invention, the flow is evaluated using a rectangular "Brett" mold, the dimensions of which are 200 cm x 20 cm x 5 cm (~ 6'6 "x 8" x 2 "). The polyurethane forming composition is formed and immediately injected into the Brett mold, which is oriented vertically (i.e. 200 cm in the vertical direction) and preheated to 45 ± 5 ° C. The composition is allowed to expand against its own weight and to harden within the mold. The amount of polyurethane forming composition is selected such that the resulting foam fills the mold. The density of the resulting foam is then measured and compared with the density of a free-lift foam manufactured from the same formulation (by injecting the formulation into a plastic bag or an open cardboard box, where it can be freely expanded in vertical and horizontal direction against atmospheric pressure). The ratio of the density of the foam of the Brett mold to the density of free development is considered to represent the "flow rate" of the formulation. With this invention, the flow index values are typically less than 1.8 and preferably vary between 1.2 and 1.5.

Preferably, the polyurethane foam exhibits a low factor k. The k factor of a foam may depend on several variables, of which density is an important variable. For many applications, a rigid polyurethane foam with a density of between 28.8 and 40 kg / m3 (1.8 to 2.5 pounds / cubic foot) exhibits a good combination of physical properties, dimensional stability and costs. The foam according to the invention, which has a density within that range, preferably exhibits a factor ka 10 ° C not greater than 22, preferably not greater than 20, and more preferably not greater than 19.5 mW / m-° K. A higher density foam may have a somewhat higher k factor.

In addition to the foams for household appliances and for thermal insulation described above, the invention is also useful for producing foams intended to soundproof vehicles, for one or more layers of a laminated board, for pipe insulation and for other products that require foams. The invention is of particular interest when rapid hardening is sought and / or when good thermal insulation properties in the foam are desired.

If desired, the processes of the invention can be carried out in conjunction with the methods described, for example, in the patent document with the number WO 07/058793, wherein the reaction mixture is injected into the cavity of a closed mold, which is under reduced pressure.

The following examples are provided to illustrate the invention, although they are not intended to limit its scope. All parts percentages are expressed by weight, unless otherwise indicated.

Example 1

A mixture of the cis and trans isomorondiamine isomers (from Sigma-Aldrich, Gillingham, United Kingdom) (5015 g, 29.5 mol) is added in a nitrogen purged glass reactor and heated to 125 ° C. The flask is pressurized at ~ 4500 kPa with propylene oxide and the pressure is maintained until a total of 5133 g (88.4 mol) of propylene oxide is introduced into the flask. The reaction digestion is then allowed to occur for two hours, at 125 ° C, after which 79.4 g of a 45% potassium hydroxide solution is incorporated. The water is removed under vacuum at 115 ° C and the reactor is reheated to 125 ° C. More propylene oxide is introduced into the reactor, at a rate of 30 g / minute, until another 4356 g (75 mol) of propylene oxide is added. Then the digestion of the reaction is again allowed for 2 hours, at which time 56.7 g of a 70% solution of acetic acid in water are added. The resulting polyol has a hydroxyl number of 440 mg of KOH / g (corresponding to an equivalent hydroxyl weight of 127.5) and a hydroxyl functionality close to 4.0. The polyol has a viscosity of 23,800 centipoise at 50 ° C.

Example 2

Rigid polyurethane foam is produced from the components described in Table 1. The foam processing is carried out using a Hi Tech CS-50 high pressure machine, operated with a productivity of 175-225 g / s. The foam formulation is injected into a bag (to measure free development density) and into a vertical Brett mold, which is preheated to 45 ° C. The temperatures of the components before mixing are ~ 21 ° C.

Table 1

 Component

 Parts by weight

 Polyol started with sorbitol1

 in -vi 0

 Polyol of Example 1

 15 6

 Polyol initiated with ethylenediamine2

 11 0

 Poly (propylene oxide) diol3

 10 0

 Component

 Parts by weight

 Water

 2.4

 Silicone surfactant

 2.0

 Amine catalysts

 2.0

 Cyclopentane

 14.0

 Polymeric MDI4 (index)

 144 (index 115)

1 A functional poly (propylene oxide) 6.0 having a hydroxyl number of 482, marketed as Voranol® RN 482 polyol, from Dow Chemical. 2 A poly (propylene oxide) having a hydroxyl number of 500, marketed as Voranol® RA 500 polyol, from Dow Chemical. 3 A diol having a molecular weight of approximately 400.5 marketed as Voranol® P400 polyol, from Dow Chemical. 4 Voranate ™ M229 polymeric MDI, marketed by Dow Chemical.

The composition has a creamy time of 3.5 seconds, a gel time of 33 seconds and a tack free time of 41 seconds. The free development density is 22.28 kg / m3, and the minimum filling density is 32.1 kg / m3. The flow rate is therefore 1,441. The foam has an average compression strength of 145.62 kPa.

The k factor is measured in 8 ”x 1” x 1 ”(20 x 2.5 x 2.5 cm) samples using a Laser Comp Fox 200 device, with a temperature of the upper cold plate of 10 ° C and a temperature of the lower hot plate of 38 ° C, and as found, is 19.15 mW / m- ° K.

Claims (10)

5 10 fifteen twenty 25 30 35 1. A process for preparing a rigid polyurethane foam, comprising the following: a) forming a reactive mixture containing at least: 1) a polyol initiated with amines or a mixture thereof with at least one other different polyol, with the proviso that said mixture contains at least 5% by weight of the polyol initiated with amines, where the polyol initiated with amines has a variable average functionality between 3.3 and 4.0 and an equivalent weight of hydroxyl of between 75 and 560, and the polyol initiated with amines is a reaction product of at least one C2-C4 alkylene oxide with an aminocylohexane-alkylamine initiator compound; 2) at least one polyether polyol having a variable functionality between 4.5 and 7 and an equivalent hydroxyl weight of 100 to 175; 3) at least one polyol started with different amines having a variable average functionality between 2.0 and 4.0 and an equivalent hydroxyl weight of between 100 and 225; 4) at least one physical hydrocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, fluorocarbon, dialkyl ether or fluorine substituted dialkyl ether blowing agent and 5) at least one polyisocyanate and b) subject the reaction mixture to conditions such that the reaction mixture expands and hardens to form a rigid polyurethane foam. 2. The process according to claim 1, wherein the reaction mixture also contains a polyol not initiated with amines, which has a variable functionality between 2.0 and 3.0 and an equivalent hydroxyl weight of between 90 and 500 3. The process according to claim 1 or claim 2, wherein the reaction mixture also contains water. 4. The process according to any of claims 1 to 3, wherein the polyol initiated with amines 1) has a functionality of 3.7 to 4.0 and an equivalent hydroxyl weight of between 100 and 130. 5. The process according to any of claims 1 to 4, wherein the aminocyclohexane-alkylamine initiator compound is represented by any of the following structures: image 1 wherein each R is independently hydrogen or C1-C4 alkyl, R1 is C1-C4 alkyl, and m is a variable number from 1 to 8. 6. The process according to any preceding claim, wherein the alkylene oxide is ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide. 7. The process according to any preceding claim, wherein the initiator compound is isophorondiamine. 8. The process according to any one of claims 1 to 6, wherein the starting compound is 1,8-diamino-p-menthane. 9. A rigid polyurethane foam manufactured according to any one of claims 1 to 4. 10. The foam according to claim 9, which is a foam for insulating an appliance, for a layer of a laminated board, for pipe insulation or for a part intended to soundproof vehicles.